v0.29.0-rc0

[borg323]

In this release:

• Initial support for attention policy, only cuda backend and partially in
  blas/dnnl/eigen (good enough for T79).
• Non multigather (legacy) search code and --multigather option are removed.
• 15b default net is now 753723.
• The onnx backend now allows selecting gpu to use.
• Improved error messages for unsupported network files.
• Some assorted fixes.

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This discussion was created from the release v0.29.0-rc0.

[Vukica14]

Hi to all which version I should use for Nvidia GTX850M ? CUDAN ?

[mooskagh]

As per https://lczero.org/play/download/, it should be a cudnn version.